Windowed oven door



Jan. 9, 1968 B. HURKO wINDowED OVEN DOOR Filedv July 14,v 196e INVENTOR. BOHDAN HuRKo H S ATTORNEY United States Patent O Y 3,362,396 WINDOWED OVEN DOR Bolidan Hurko, Louisville, Ky., assignor to General Electric Company, a corporation of New York Filed July 14, 1966, Ser. No. 565,310 10 Claims. (Cl. 126-200) ABSTRACT F THE DISCLOSURE A high temperature oven such as is capable of normal baking operations as Well as a high temperature self-cleaning pyrolytic cycle for cleaning the oven walls of deposited food soil and grease spatter. The oven has a front-opening access door with transparent window panes for viewing the food while it is being cooked. The door is formed with separable elements and a removable reflective shield built therein so that when the door elements are separated the reflective shield may be moved either into one position obstructing the view through the window or a second position hidden within the door structure. Releasable latching means are provided for holding the door elements together, and thermally responsive means are carried by the door to render the releasable latching means inoperable whenever the oven temperature rises above the normal cooking temperatures of about 550 F. The reflective shield has an actuator arm that cooperates with an interlock switch means mounted in the oven housing so that movement of the shield to a view obstructing position moves the actuator arm to operate the switch means as well as latches the door closed to the oven housing.

The present invention relates to windowed doors and particularly to an improved windowed door for use with high temperature ovens, such as self-cleaning baking ovens wherein the oven wall temperatures may reach as high as 950 to 1000 F.

Over the years housewives have become accustomed to having windowed oven doors so that they may observe food being cooked in the oven without having to open the oven door. With the advent of the invention set forth in my Patent 3,121,158, assigned to General Electric Company, the assignee of this application, it became possible for housewives to have self-cleaning ovens which are cleaned by a pyrolysis process during which the temperature in the oven is raised well above the normal cooking range, usually to between about 750 F. and about 950 F. Initially, windowed oven doors were sacrificed as the price one had to pay for gaining the more important automatic self-cleaning feature. The invention of Howard Baughman and Kermit Keeling, Sr., copending application Ser. No. 515,910, iiled Dec. 23, 1965, and assigned to General Electric Company, now Patent No. 3,311,106, made it possible for the iii-st time to have a self-cleaning oven with a windowed door.

When heat cleaning an oven having a windowed door, it is desirable to provide a cooling air passage between the inner and outer panels of the door to insure that the door does not become uncomfortably hot to the human touch. Such a cooling air passage might be a disadvantage during normal cooking operations as moisture can be drawn into the passage and condense on the window, thus obscuring the users view into the oven. This is a particularly acute problem with eye-level ovens because the housewife often cooks some foods on surface units below the oven at the same time she is using the oven. The vapors generated in the surface unit cooking operations accentuate the fogging condition of the oven window.

For safety reasons it is desirable to insure that the selfcleaning process cannot be started unless the oven door is 3,362,390 Patented `ian. 9, 1968 ICC fully closed and locked, and that the door cannot be opened when the temperature within the oven is above normal cooking temperatures. To these ends, self-cleaning ovens normally have an electrical control circuit for the self-cleaning heating means including an electrical interlock switch which is normally open to prevent activation of the heating means into a high temperature cycle unless certain criteria are met. The switch is closed as a result of moving the door to its fully closed, self-cleaning conguration so that the heating means can be activated.

A manual latch mechanism is normally provided for self-cleaning ovens to hold the door closed, and the mechanism is locked in its closed position when the oven temperature is above the normal cooking range. The patent to Roy Chisholm, No. 3,214,567, assigned to General Electric Company, illustrates one such electrical control circuit and latch mechanism arrangement.

It is an object of this invention to provide an improved windowed door for use with high temperature ovens including a reilective shield which is moved into position to cover the window during high temperature cleaning operations by temporarily separating certain parts of the door and gaining access to the shield.

It is another object of this invention to provide an improved oven door which includes a window for viewing the interior of the oven during normal cooking operations, an air passage between the inner and outer portions of the door, and a reilective shield for alternatively covering the window during high temperature operations and blocking the air passage during normal temperature operations.

It is a further object of this invention to provide an improved windowed door including an arrangement of parts for operating the ovens electrical control circuit interlock switch to insure that high temperature operation can begin only when the door is in a fully closed and locked position and the reflective shield is also in a position to cover the window.

It is a still further object of this invention to provide an improved windowed door having separable parts and including an improved arrangement for securely latching the door from being separated whenever the oven temperature is above substantially the normal cooking temperature range.

The present invention in accordance with one form thereof, is embodied in a door construction for a high temperature oven having an oven cavity formed by a box-like oven liner and a front-opening, windowed access door. The door includes an inner door liner and a separable outer door panel with the outer door panel being movable between a rst position overlying the inner door liner and a second position moved away from the inner door liner. The door also includes a reilective shield movable between a first position exposing the window and a second position covering the window. The outer door panel allows movement of the shield only when the outer door panel is in its said second position. The oven also has an electrical control circuit for the oven heating means including an interlock switch which must be closed for the heating means to be activated for a high temperature self-cleaning operation, as is usual in the art. The front edge of the oven housing includes an opening with the interlock switch mounted adjacent an edge of the opening on the opposite side of the housing from the door mounting means. The door includes a switch actuator which is rotatably mounted for movement through an opening in the housing so as to engage the switch and close it. This movement of the actuator also brings it into an interfering relationship with the oven housing to hold the inner door liner closed. The shield and actuator are cooperatively mounted so that, as the shield is moved to its window covering position, it moves the actuator into engagement with the switch and also into an interfering or locking relationship with the oven housing. The door further includes a latch means normally holding the outer door panel in its position overlying the inner door liner and manually movable to release the outer door panel. The door also has a temperature responsive blocking means mounted to be exposed to the heat in the oven and moving in response to a predetermined high oven temperature to a position preventing movement of the latch means so that the outer door panel cannot be separated from the inner door liner.

My invention will be better understood from the following description taken in conjunction with the accompanying drawing and its scope will be pointed out in the appended claims.

FIGURE 1 is a front elevational view of an oven with a windowed door embodying the present invention, the view being partly broken away and partially in section for purposes of illustration;

FIGURE 2 is a right side view on an enlarged Scale taken along line 2 2 of FIGURE 1; and

FIGURE 3 is a right side view similar to FIGURE 2 taken along line 3-3 of FIGURE 1.

Turning now to a consideration of the drawings, there is shown for illustrative purposes an oven of the type usually provided as an eye-level electric oven. Of course, this invention is not limited to use in electric eye-level ovens. The oven could be heated by gas, it could be a built-in oven, an oven of a free-standing range or any other type of high temperature heated oven.

The oven includes an oven cavity 11 formed by a boxlike oven liner 12 and a front-opening access door 13. In the usual way, the oven liner 12 is supported within an oven housing or appearance cabinet 14 with the space between the appearance cabinet and oven liner being filled with a body of suitable thermal insulation 15. The oven cavity is supplied with two standard heating elements; namely, a lower baking element 16 and an upper broiling element 17. Additionally, a low wattage mullion or perimeter heater 18 encircles the front portion of the oven liner 12 as is seen in FIGURE 2 so as to provide generally uniform oven wall temperatures throughout the oven. This heater 13 and its function are more fully described in my aforementioned Patent 3,121,158.

To one side of the oven cavity, there are provided, as is seen in FIGURE 1, controls 19 such as an oven selector switch, a thermostat and an oven timer for forming appropriate connections within the electrical control circuit for the oven so as to control both normal cooking operations and the oven cleaning cycle. There are a number of suitable control circuits for the oven, one of which has been shown and described in the aforementioned `Chisholm Patent No. 3,214,567. Thus, for the sake of simplicity, a complete control circuit is not shown here- As best seen in FIGURES 2 and 3, the oven door 13 is of generally sheet metal construction having two main elements; a decorative, outer door panel 20 and an inner door liner 21. The outer door panel 20 is of a shallow, pan-shaped construction by virtue of the fact that it has a rearwardly-turned peripheral flange 22. The inner door liner 21 is of a closed container contiguration having three main components; namely, an outer member 23 with a rearwardly-turned peripheral iiange 24, an intermediate member with a forwardly-turned peripheral flange 26 which mates with the rearward flange 24 of the outer member, and an inner member 27, attached to the intermediate member around its periphery by any suitable means such as spaced screws. The inner member 27 covers an area which is slightly less than the area of the front edge of the oven liner 12 and is adapted to be received within the oven liner when the door is in its closed position. A high temperature gasket 23 is sandwiched between the intermediate member 25 and the periphery of the inner member 27 so as to firmly contact the front edge of oven liner 12 when the door is in its closed position to effectively seal the oven cavity 11. The space confined lwithin the inner door liner 21 is lled with a body 29 of suitable thermal insulation.

The door 13 is shown mounted along its left side for pivotal movement about a vertical axis between the door closed position shown in FIGURES 2 and 3 `and a door open position exposing the oven cavity 11. For this purpose, brackets 30 are attached to the oven housing 14 above and below the door 13 and include vertical hinge pins 31 which project through mating openings in the flanges 22, 24 and 26 as is best seen in FIGURE 2. For ease of operation and long life, bearings 32 of a low Vfriction material may be provided between the brackets 30 and the ange 22 and between the flange 22 and the ange 24. The lower edge of flange 22 is provided with a handle 33 which may be grasped by the user for opening and closing the door. The inner door liner 21 is releasably held in its closed position by an arrangement including a stud 34 mounted on the inner door liner 21 and a mating spring clip 35 mounted in an opening in the oven housing 14 as is best seen in FIGURE 3.

In order normally to restrain the outer door panel 2t) in a position overlying inner door liner 21, a latch means is provided including a bracket 36 which is mounted on the inner side of the outer door panel and supports a pin 37. The pin extends downwardly through an appropriate opening in the edge of flange 22 of the outer door panel 20. Pin 37 is provided with a cut-away portion 38 in its side which is adapted to engage a mating tang 39 secured to the inner door liner 21. A coil spring 40 is mounted between bracket 36 and a shoulder 41 provided on the pin 37 so as to bias the cut-away portion 3S into engagement with the tang 39, thus normally holding the outer door panel 20 and inner door liner 21 in an overlying relationship for movement together in response to a force exerted on handle 33. The pin 37 is slidably mounted in the bracket 36 and its cooperating opening through flange 22 so that the user may press upwardly on pin 37 and pull outwardly on handle 33 to swing the outer door panel 20 to a position away from the inner door liner 21 in the manner of opening the front cover of a book, while the stud 34 and spring clip 3S arrangement retains the inner door liner in its closed position.

The door is provided with a transparent section so that the housewife may view the interior of the oven cavity 11 during normal cooking operations without having to open the door. To this end, there is a relatively large window opening 42 in the outer door panel 20 and a relatively small window opening 43 in the inner door liner 21. A single glass pane 44 is mounted in the window opening 42. However, it is well to provide a plurality of glass panes or sheets in the opening 43 with a dead air space therebetween so as to improve the thermal insulation and retard heat ilow through the inner door liner. Moreover, it is well to provide for the sealing of the inner door liner 21 yso as to prevent the escape of odors and vapors, as well as convection currents of air. To this end, a pair of glass sheets or panes 45 and 46 are assembled on a continuous spacer frame 47 which completely encloses the peripheral edge of the glass panes and fits closely around the edges of outer member 23 and inner member 27 of inner panel 21 forming the opening 43. Normally, the opening 43 occupies only a portion of inner door liner 21, being just suicient in size to provide a good View of the oven cavity 11. The opening 42 and glass pane 44 in outer door panel 20 need be only as large as the window opening 43; however, for decorative purposes and ease of cleaning, the opening 42 and pane 44 are normally made somewhat larger, in fact almost as large as the outer door panel 20. Then, a decorative coating 48 is applied to the rear surface of the glass pane 44 so as to cover all but a central area in alignment with the window opening 43.l

During the high temperature, self-cleaning operation it is desirable to interpose a reiiective shield over the outside of opening 43. Such a shield will prevent the escape of much of the radiant energy from within the oven cavity. This serves to increase the operating temperature of glass pane or sheet 46 and thereby automatically decompose the food soil from the inner surface thereof during the high temperature heat cleaning operation. On the other hand, this shield must be removed from covering the opening 43 during normal cooking operations if the user is to be able to see within the oven cavity 11. During heat cleaning operations it also is desirable to form a cooling air passage from the bottom to the top of the door between outer door panel 20 and inner door liner 21 so that a chimney effect will be created to cause a stream of air to ow therebetween. This insures that the temperature of the outer door panel 20 remains sufficiently low to be comfortable to the touch during high temperature heat cleaning operations. On the other hand, during normal cooking operations, such an air passage is undesirable as the air flowing through the passage may contain moisture which will condense on glass panes 44 and 45 and obscure the users View of the oven cavity. This moisture condensation problem is particularly acute in eye-level ovens because surface units are normally mounted below the oven and it quite often happens that the housewife will use both the oven and the surface units at the same time. The cooking operations being conducted on the surface units frequently generate vapors which will be carried up within the passage in the oven door and accentuate the condensation problem.

In order to provide an air passage, the outer door panel, in its overlying position, is spaced slightly away from the inner door liner and entrance and exhaust openings 49 and 50 are spaced along the lower and upper portions respectively of flange 22 as is best seen in FIG- URE 2. In order alternately to provide a reflective shield for window opening 43 or to block the air passage, I further provide a pair of brackets 51 mounted adjacent the sides of the outer member 23 of inner door liner 21 as is seen in FIGURE 2. I also provide a shield arrangement including a rod 52 and a metal shield member 53 such as stainless steel or aluminum, with the shield member firmly attached to the rod in some suitable manner such as crimping or welding. The shield member 53 includes a base portion 54, normally lying parallel to outer member Z3 and a resilient lange portion 55 extending substantially perpendicular to the base portion 54. The shield arrangement is pivotally mounted by means of the rod 52 and the brackets 51 so as to have a first extreme position exposing the windowed opening 43 as seen in FIGURE 2, and a second extreme position covering the window opening as seen in FIGURE 3. In its rst extreme position, which is for a normal cooking operation, the windowed unit 43 is exposed and the iiange 55 covers the air entrance openings 49 in the lower edge of outer door panel 20, thus blocking the air passage between the inner door panel and inner door liner to prevent condensation or fogging of the glass panes 44 and 4S. In its second extreme position, for the heat cleaning operation, the base 54 of the shield covers window opening 43 and the iiange 55 is received in a recess 56 provided in outer member 23 so that the shield may be substantially parallel to the inner door liner 21.

It will be noted that the normal spacing between the outer door panel 20 and inner door liner 21 is insufficient to allow pivotal movement of the shield through substantially 180 between its two extreme positions. Thus, the shield may be moved between its extreme positions only when the pin 37 has been released from the tang 39 and the outer door panel 20 pivoted Aaway from the inner door liner 21. Subsequent return of the outer door panel to its position overlying the inner door liner serves to hold 6 the shield in the selected one of its two extreme positions.

It is desirable to provide an interlock switch for the control circuit which insures that the heating elements may not be energized for a high temperature heat cleaning cycle unless the oven door is in its fully closed7 self-cleaning position. To this end, I provide the oven housing or appearance cabinet 14 with `an opening -57 shown in FIG- URE 3 in alignment with one end of pivot rod 52, and I mount an electrical interlock switch 58 on the inside of housing 14 adjacent the opening 57. I further provide an actuator or operating arm 59 which is freely mounted for pivotal movement on the rod 52 of the reflective shield 53 so that the Iactuator may extend through the opening 57. The protruding end of the actuator 59 is provided with a hook portion 6) which extends downwardly in the position shown in FIGURE 3 so as to be in interfering and locking relationship with a portion of the edge of housing 14 forming opening 57 and to contact and actuate switch 58. The actuator 59 is provided with a pair of spaced stop members separated by an angle of about 61 and `62, and the rod S2 is provided with a tab 63 to engage the stop members in a lost motion relationship and thus 4move the actuator through an angle of about 90 when the shield is moved between its extreme positions of In order to insure that the door is in its fully closed position before the heaters can be activated into a high temperature heat cleaning operation, the switch 58 is of the type which is spring loaded to a normally open position so that the mere weight of actuator 59 will not close the switch. Additionally, shield member 53 is provided with an embossment 55a adjacent each of its side edges as is seen in FIGURE 3. These embossments extend in a direction opposite to the ange 55 so that outer door panel 20 will engage the embossments and rmly push the shield into its extreme position over widow opening 43 without blocking the How of air through the door. Since the shield member 53 is firmly attached to the rod 52, this movement rotates the rod and tab 63 and the rod bears against stop member l61 on the actuator 59 to force the actuator into its extreme position shown in solid line in FIGURE 3. This pressure on actuator 59 is sufficient to close -switch 58. When the shield 53 is rotated to its other extreme position exposing the window opening 43 as shown in FIGURE 2 the tab 63 engages the stop member 62 and rotates the actuator out through the opening 57 to the position shown in broken line in FIGURE 3. When the actuator is thus rotated the electrical interlock switch 5S opens and the heating units may not be energized for a high temperature heat cleaning operation.

It will be obvious that, should the shield member 53 extend to the vicinity of the actuator 59, the tab 63 could be provided on the shield member rather than on the rod. Also, it will be noted that switch 58 is mounted fairly close to oven liner 12, which reaches a rather high temperature. If it is desired to have switch 58 in a lower temperature environment, the switch couldbe mounted further away from the liner and include a lever or ar-m extending inwardly to be engaged by the actuator '59. The arrangement of parts thus far described allows energization of the heating elements of the range for a heat cleaning cycle only when the door is in its fully closed, self-cleaning position and the reflective shield in its raised, window covering position.

It also is highly desirable that the door be so constructed that it is impossible for the user to separate the door elements at any time when the temperature within the oven cavity is above substantially the normal maximum cooking temperature of about 550 F. To this end, as seen in FIGURE 3, I provide a temperature responsive blocking means including a bimetal strip 64 mounted at one end to the inner member 27 of the inner door panel 21 so as to be exposed to the heat in the oven cavity. The other end of the bimetal strip carries a pin 65 which normally barely extends out of the outer member 23 of the inner door panel 21. The bimetal bends in response to a predetermined high temperature of the oven, just above the upper limit of the normal cooking range, so as to extend the pin l65 outwardly across the top of latch pin 37. This blocks the vertical movement of the latch pin, so that, as long as the temperature within the oven is above this predetermined level, the latch 37 may not be moved in such a manner as to allow separation of the outer door panei away from the inner door liner.

The foregoing is a description of an illustrative embodiment of the invention and it is my intention in the appended claims to cover all forms which fall within the scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An oven door of hollow metal construction includin an inner door liner and an outer door panel; said outer door panel being mounted for movement between an open position away from said inner door linear and a closed position in which it overlies said inner door liner; said inner door liner and outer door panel having normally aligned transparent viewing sections; said door also including a reflective shield mounted for movement between a first position exposing said transparent section of said inner door liner and a second position covering said transparent section of said inner door liner; said outer door panel being adapted to allow movement of said shield between its position only when said outer door panel is in its open position.

2. An oven door of hollow metal construction including an inner door liner and an outer door panel; said outer door panel being pivotally mounted for movement between an open position in which it projects from said inner door liner and a closed position in which it overlies said inner door liner; said inner door liner and outer door panel having normally aligned transparent viewing sections; said door also including a reflective shield pivotally mounted for movement between a first extreme position exposing said transparent section of said inner door liner on a second extreme position -covering said transparent section of said inner door liner; said outer door panel being adapted to allow movement of said shield between its extreme positions only when said outer door panel is in its open position.

3. A high temperature oven including a housing having an oven cavity formed therein by a box-like oven liner and a front-opening access door; heating means for the oven and an electrical control circuit for the heating means including an interlock switch to prevent activation of the heating means and to allow activation of the heating means when closed said door having an inner door liner and an outer door panel; said outer door panel being pivotally mo'unted for movement between an open position in which it projects from said inner door liner and a closed position in which it overlies said inner door liner; said inner door liner and outer door panel, having normally aligned transparent viewing sections; said door also including a reflective shield mounted for movement between a lirst extreme position exposing said transparent section of said inner door liner and a second extreme position covering said transparent section of said inner door liner; the oven housing having an opening therein; said door including a switch actuator mounted so that movement of said shield to its second extreme position causes said actuator to move inwardly through the opening so as to close the interlock switch and to be in an interfering relationship with the housing to secure said inner door liner closed, while movement of said shield to its first extreme position causes said actuator to move outwardly through the opening so as to open the switch and to release said inner door liner; said outer door panel allowing movement of said shield between its extreme positions only when said outer door panel is in its open position.

4. An oven as set forth in claim 3 further including an air passage between said inner door liner and said outer door panel, said passage including an air inlet openlng adjacent one edge of said outer door panel; and wherein said reilective shield has means that is adapted to block said opening when said shield is in its first extreme position.

5. An oven as set forth in claim 3 further including latch means normally retaining said outer door panel in its closed position with said inner door liner; said latch means being manually movable to an unlatched position in which it allows said outer door panel to move to its open position away from the inner door panel; and temperature responsive blocking means mounted on said door so as to be exposed to the heat in the oven, said blocking means moving in response to a predetermined high temperature of the oven to a position preventing movement of said latch means to its unlatched position.

6. A high temperature oven including a housing having an oven cavity formed therein by a box-like oven liner and a front-opening access door; heating means for the oven, and an electrical control circuit for the heating means; said door having a pivoted inner door liner and a pivoted outer door panel movable between open and closed positions; a latch means normally holding said inner door liner and said outer door panel for movement together, said latch means being manually movable to an unlatched position in which it allows said outer door panel to move to its open position with said inner door liner remaining in its closed position; said inner door liner and outer door panel including normally aligned transparent viewing sections; a rellective shield pivotally mounted between said inner door liner and said outer door panel for movement between a rst extreme position in which said transparent section of said inner door liner is exposed and a second extreme position in which it covers said transparent section of said inner door liner; said outer door panel being adapted to allow movement of said shield from its lirst to its second extreme position only when said outer door panel is in its open position; subsequent movement of said outer door panel to its closed position causing said shield to be held in its second extreme position.

7. An oven as set forth in claim 6 wherein the control circuit includes a switch mounted on a side of the housing opposite said door, the switch being biased to an open position to prevent activation of the heating means and movable to a closed position to allow activation of the heating means; the housing including an opening therein; said inner door liner further including a pivotally mounted switch actuator engageable by said shield to be moved inwardly through the opening in the housing to a position in which it closes the switch and is in an interfering relationship with the housing when said shield is moved to its second extreme position, said switch actautor being engageable by said shield to be moved outwardly through the opening in the housing to a position in which it allows the switch to open and is out of its interfering relationship with the housing when said shield is moved toward its rst extreme position.

8. An oven as set forth in claim 6 wherein said inner door liner and outer door panel form an air passage therebetween including an opening in said outer door panel adjacent one edge thereof and said reflective shield has means that is adapted to block said opening when in its lirst extreme position.

9. An oven as set forth in claim 6 wherein said door includes temperature responsive blocking means mounted to `be exposed to the heat in the oven; said blocking means moving in response to a predetermined high temperature of the oven to a position preventing movement of said latch means to its unlatched position.

10. A high temperature oven having a housing, an oven cavity formed therein by a box-like oven liner and a front-opening access door; heating means for the oven and an electrical control circuit for the heating means; said door having a pivotal inner door liner and a pivoted outer door panel movable between open and closed positions; a latch means normally holding said inner door liner and said outer door panel for movement together, said latch means being manually movable to an unlatched position in which it allows said outer door panel to move to its open position away from said inner door liner; said inner door liner and said outer door panel including normally aligned transparent Viewing sections; a reflective shield pivotally mounted between said inner door liner and said outer door panel for movement between a first extreme position in which said transparent section of said inner door liner is exposed and a second extreme position in which it covers said transparent section of said inner door liner; said outer door panel being adapted to allow movement of said shield from its first to its second extreme position only when said outer door panel is in its open position; subsequent movement of said outer door panel to its closed position causing said shield to be held in its second extreme position; the electrical control circuit including a switch mounted on the side of the housing opposite said door, the switch being biased to an open position to prevent activation of the heating means and movable to a closed position to allow activation of the heating means; the housing including an opening therein; said inner door liner also including a pivotally mounted switch actuator engageable by said shield to be moved inwardly through the opening in the housing toa position in which it closes the switch and is in an interfering relationship with the housing when said shield is moved to its second extreme position, said actuator being engageable by said shield to be moved outwardly thro-ugh the opening in the housing to a position in which it allows the switch toV open and is out of its interfering relationship with the housing when said shield is moved toward its rst extreme position; and said door also` including temperature responsive blocking means mounted to be eX- posed to the heat in the oven; said blocking means moving in response to a pre-determined high temperature of the oven to a position preventing movement of said latch means to its unlatched position.

References Cited UNITED STATES PATENTS 2,963,019 12/1960 Domsky 126-200 3,088,453 5/1963 Grahn et al. 126-200 X 3,177,334 4/1965 Kinkle 126-200 X KENNETH W. SPRAGUE, Primary Examiner. 

